diff --git a/peripconn.go b/peripconn.go
index 2568477..cf8e986 100644
--- a/peripconn.go
+++ b/peripconn.go
@@ -51,12 +51,16 @@ func (c *perIPConn) Close() error {
 }
 
 func getUint32IP(c net.Conn) uint32 {
+	return ip2uint32(getConnIP4(c))
+}
+
+func getConnIP4(c net.Conn) net.IP {
 	addr := c.RemoteAddr()
 	ipAddr, ok := addr.(*net.TCPAddr)
 	if !ok {
-		return 0
+		return net.IPv4zero
 	}
-	return ip2uint32(ipAddr.IP.To4())
+	return ipAddr.IP.To4()
 }
 
 func ip2uint32(ip net.IP) uint32 {
diff --git a/server.go b/server.go
index afc2147..f21fec3 100644
--- a/server.go
+++ b/server.go
@@ -2,6 +2,7 @@ package fasthttp
 
 import (
 	"bufio"
+	"errors"
 	"fmt"
 	"io"
 	"log"
@@ -131,7 +132,7 @@ type RequestCtx struct {
 
 	logger ctxLogger
 	s      *Server
-	c      io.ReadWriter
+	c      io.ReadWriteCloser
 	fbr    firstByteReader
 
 	// shadow is set by TimeoutError().
@@ -144,7 +145,7 @@ type RequestCtx struct {
 }
 
 type firstByteReader struct {
-	c        io.ReadWriter
+	c        io.ReadWriteCloser
 	ch       byte
 	byteRead bool
 }
@@ -285,7 +286,7 @@ func (s *Server) Serve(ln net.Listener) error {
 // ServeConcurrency blocks until the given listener returns permanent error.
 // This error is returned from ServeConcurrency.
 func (s *Server) ServeConcurrency(ln net.Listener, concurrency int) error {
-	ch := make(chan net.Conn, 16*concurrency)
+	ch := make(chan net.Conn, 2*concurrency)
 	stopCh := make(chan struct{})
 	go connWorkersMonitor(s, ch, concurrency, stopCh)
 	var lastOverflowErrorTime time.Time
@@ -338,16 +339,13 @@ func connWorkersMonitor(s *Server, ch <-chan net.Conn, maxWorkers int, stopCh <-
 }
 
 func connWorker(s *Server, ch <-chan net.Conn) {
-	var c net.Conn
 	defer func() {
 		if r := recover(); r != nil {
 			s.logger().Printf("panic: %s\nStack trace:\n%s", r, debug.Stack())
 		}
-		if c != nil {
-			c.Close()
-		}
 	}()
 
+	var c net.Conn
 	var tc *time.Timer
 	for {
 		select {
@@ -362,14 +360,12 @@ func connWorker(s *Server, ch <-chan net.Conn) {
 				return
 			}
 		}
-		s.ServeConn(c)
-		c.Close()
+		s.serveConn(c)
 		c = nil
 	}
 }
 
 func acceptConn(s *Server, ln net.Listener, lastPerIPErrorTime *time.Time) (net.Conn, error) {
-	maxConnsPerIP := s.MaxConnsPerIP
 	for {
 		c, err := ln.Accept()
 		if err != nil {
@@ -383,32 +379,40 @@ func acceptConn(s *Server, ln net.Listener, lastPerIPErrorTime *time.Time) (net.
 			}
 			return nil, err
 		}
-		if maxConnsPerIP > 0 {
-			ip := getUint32IP(c)
-			if ip == 0 {
-				return c, nil
-			}
-			n := s.perIPConnCounter.Register(ip)
-			if n > maxConnsPerIP {
+		if s.MaxConnsPerIP > 0 {
+			pic := wrapPerIPConn(s, c)
+			if pic == nil {
+				c.Close()
 				if time.Since(*lastPerIPErrorTime) > time.Minute {
-					s.logger().Printf("Too many connections from ip %s: %d. MaxConnsPerIP=%d",
-						uint322ip(ip), n, maxConnsPerIP)
+					s.logger().Printf("The number of connections from %s exceeds MaxConnsPerIP=%d",
+						getConnIP4(c), s.MaxConnsPerIP)
 					*lastPerIPErrorTime = time.Now()
 				}
-				c.Close()
-				s.perIPConnCounter.Unregister(ip)
 				continue
 			}
-			return &perIPConn{
-				Conn:             c,
-				ip:               ip,
-				perIPConnCounter: &s.perIPConnCounter,
-			}, nil
+			return pic, nil
 		}
 		return c, nil
 	}
 }
 
+func wrapPerIPConn(s *Server, c net.Conn) net.Conn {
+	ip := getUint32IP(c)
+	if ip == 0 {
+		return c
+	}
+	n := s.perIPConnCounter.Register(ip)
+	if n > s.MaxConnsPerIP {
+		s.perIPConnCounter.Unregister(ip)
+		return nil
+	}
+	return &perIPConn{
+		Conn:             c,
+		ip:               ip,
+		perIPConnCounter: &s.perIPConnCounter,
+	}
+}
+
 var defaultLogger = log.New(os.Stderr, "", log.LstdFlags)
 
 func (s *Server) logger() Logger {
@@ -418,11 +422,33 @@ func (s *Server) logger() Logger {
 	return defaultLogger
 }
 
+// ErrPerIPConnLimit may be returned from ServeConn if the number of connections
+// per ip exceeds Server.MaxConnsPerIP.
+var ErrPerIPConnLimit = errors.New("too many connections per ip")
+
 // ServeConn serves HTTP requests from the given connection.
 //
 // ServeConn returns nil if all requests from the c are successfully served.
 // It returns non-nil error otherwise.
-func (s *Server) ServeConn(c io.ReadWriter) error {
+//
+// Connection c must immediately propagate all the data passed to Write()
+// to the client. Otherwise requests' processing may hang.
+//
+// ServeConn closes c before returning.
+func (s *Server) ServeConn(c io.ReadWriteCloser) error {
+	conn, ok := c.(net.Conn)
+	if ok {
+		pic := wrapPerIPConn(s, conn)
+		if pic == nil {
+			c.Close()
+			return ErrPerIPConnLimit
+		}
+		c = pic
+	}
+	return s.serveConn(c)
+}
+
+func (s *Server) serveConn(c io.ReadWriteCloser) error {
 	var rd readDeadliner
 	readTimeout := s.ReadTimeout
 	if readTimeout > 0 {
@@ -553,6 +579,11 @@ func (s *Server) ServeConn(c io.ReadWriter) error {
 		ctx.Logger().Printf("Error when serving network connection: %s", err)
 	}
 	s.releaseCtx(ctx)
+
+	err1 := c.Close()
+	if err == nil {
+		err = err1
+	}
 	return err
 }
 
@@ -671,7 +702,7 @@ func releaseWriter(ctx *RequestCtx, w *bufio.Writer) {
 
 var globalCtxID uint64
 
-func (s *Server) acquireCtx(c io.ReadWriter) *RequestCtx {
+func (s *Server) acquireCtx(c io.ReadWriteCloser) *RequestCtx {
 	v := s.ctxPool.Get()
 	var ctx *RequestCtx
 	if v == nil {
diff --git a/server_test.go b/server_test.go
index 68994eb..28a2c8d 100644
--- a/server_test.go
+++ b/server_test.go
@@ -279,10 +279,14 @@ func TestServerRemoteAddr(t *testing.T) {
 }
 
 type readWriterRemoteAddr struct {
-	rw   io.ReadWriter
+	rw   io.ReadWriteCloser
 	addr net.Addr
 }
 
+func (rw *readWriterRemoteAddr) Close() error {
+	return rw.rw.Close()
+}
+
 func (rw *readWriterRemoteAddr) Read(b []byte) (int, error) {
 	return rw.rw.Read(b)
 }
@@ -414,6 +418,10 @@ type readWriter struct {
 	w bytes.Buffer
 }
 
+func (rw *readWriter) Close() error {
+	return nil
+}
+
 func (rw *readWriter) Read(b []byte) (int, error) {
 	return rw.r.Read(b)
 }